aboutsummaryrefslogtreecommitdiffstats
path: root/arch/sparc64/kernel/kprobes.c
blob: b95984154dbad1427701e6c97a46e7bcfa5b014d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
/* arch/sparc64/kernel/kprobes.c
 *
 * Copyright (C) 2004 David S. Miller <davem@davemloft.net>
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <asm/kdebug.h>
#include <asm/signal.h>
#include <asm/cacheflush.h>

/* We do not have hardware single-stepping on sparc64.
 * So we implement software single-stepping with breakpoint
 * traps.  The top-level scheme is similar to that used
 * in the x86 kprobes implementation.
 *
 * In the kprobe->ainsn.insn[] array we store the original
 * instruction at index zero and a break instruction at
 * index one.
 *
 * When we hit a kprobe we:
 * - Run the pre-handler
 * - Remember "regs->tnpc" and interrupt level stored in
 *   "regs->tstate" so we can restore them later
 * - Disable PIL interrupts
 * - Set regs->tpc to point to kprobe->ainsn.insn[0]
 * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
 * - Mark that we are actively in a kprobe
 *
 * At this point we wait for the second breakpoint at
 * kprobe->ainsn.insn[1] to hit.  When it does we:
 * - Run the post-handler
 * - Set regs->tpc to "remembered" regs->tnpc stored above,
 *   restore the PIL interrupt level in "regs->tstate" as well
 * - Make any adjustments necessary to regs->tnpc in order
 *   to handle relative branches correctly.  See below.
 * - Mark that we are no longer actively in a kprobe.
 */

DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
	return 0;
}

void __kprobes arch_copy_kprobe(struct kprobe *p)
{
	p->ainsn.insn[0] = *p->addr;
	p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
	p->opcode = *p->addr;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
	*p->addr = BREAKPOINT_INSTRUCTION;
	flushi(p->addr);
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
	*p->addr = p->opcode;
	flushi(p->addr);
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
}

static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
	kcb->prev_kprobe.kp = kprobe_running();
	kcb->prev_kprobe.status = kcb->kprobe_status;
	kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
	kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
}

static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
	kcb->kprobe_status = kcb->prev_kprobe.status;
	kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
	kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
}

static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
				struct kprobe_ctlblk *kcb)
{
	__get_cpu_var(current_kprobe) = p;
	kcb->kprobe_orig_tnpc = regs->tnpc;
	kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
}

static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
			struct kprobe_ctlblk *kcb)
{
	regs->tstate |= TSTATE_PIL;

	/*single step inline, if it a breakpoint instruction*/
	if (p->opcode == BREAKPOINT_INSTRUCTION) {
		regs->tpc = (unsigned long) p->addr;
		regs->tnpc = kcb->kprobe_orig_tnpc;
	} else {
		regs->tpc = (unsigned long) &p->ainsn.insn[0];
		regs->tnpc = (unsigned long) &p->ainsn.insn[1];
	}
}

static int __kprobes kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *p;
	void *addr = (void *) regs->tpc;
	int ret = 0;
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	if (kprobe_running()) {
		/* We *are* holding lock here, so this is safe.
		 * Disarm the probe we just hit, and ignore it.
		 */
		p = get_kprobe(addr);
		if (p) {
			if (kcb->kprobe_status == KPROBE_HIT_SS) {
				regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
					kcb->kprobe_orig_tstate_pil);
				unlock_kprobes();
				goto no_kprobe;
			}
			/* We have reentered the kprobe_handler(), since
			 * another probe was hit while within the handler.
			 * We here save the original kprobes variables and
			 * just single step on the instruction of the new probe
			 * without calling any user handlers.
			 */
			save_previous_kprobe(kcb);
			set_current_kprobe(p, regs, kcb);
			p->nmissed++;
			kcb->kprobe_status = KPROBE_REENTER;
			prepare_singlestep(p, regs, kcb);
			return 1;
		} else {
			p = __get_cpu_var(current_kprobe);
			if (p->break_handler && p->break_handler(p, regs))
				goto ss_probe;
		}
		/* If it's not ours, can't be delete race, (we hold lock). */
		goto no_kprobe;
	}

	lock_kprobes();
	p = get_kprobe(addr);
	if (!p) {
		unlock_kprobes();
		if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
			/*
			 * The breakpoint instruction was removed right
			 * after we hit it.  Another cpu has removed
			 * either a probepoint or a debugger breakpoint
			 * at this address.  In either case, no further
			 * handling of this interrupt is appropriate.
			 */
			ret = 1;
		}
		/* Not one of ours: let kernel handle it */
		goto no_kprobe;
	}

	/*
	 * This preempt_disable() matches the preempt_enable_no_resched()
	 * in post_kprobes_handler()
	 */
	preempt_disable();
	set_current_kprobe(p, regs, kcb);
	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
	if (p->pre_handler && p->pre_handler(p, regs))
		return 1;

ss_probe:
	prepare_singlestep(p, regs, kcb);
	kcb->kprobe_status = KPROBE_HIT_SS;
	return 1;

no_kprobe:
	return ret;
}

/* If INSN is a relative control transfer instruction,
 * return the corrected branch destination value.
 *
 * The original INSN location was REAL_PC, it actually
 * executed at PC and produced destination address NPC.
 */
static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
					       unsigned long pc,
					       unsigned long npc)
{
	/* Branch not taken, no mods necessary.  */
	if (npc == pc + 0x4UL)
		return real_pc + 0x4UL;

	/* The three cases are call, branch w/prediction,
	 * and traditional branch.
	 */
	if ((insn & 0xc0000000) == 0x40000000 ||
	    (insn & 0xc1c00000) == 0x00400000 ||
	    (insn & 0xc1c00000) == 0x00800000) {
		/* The instruction did all the work for us
		 * already, just apply the offset to the correct
		 * instruction location.
		 */
		return (real_pc + (npc - pc));
	}

	return real_pc + 0x4UL;
}

/* If INSN is an instruction which writes it's PC location
 * into a destination register, fix that up.
 */
static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
				  unsigned long real_pc)
{
	unsigned long *slot = NULL;

	/* Simplest cast is call, which always uses %o7 */
	if ((insn & 0xc0000000) == 0x40000000) {
		slot = &regs->u_regs[UREG_I7];
	}

	/* Jmpl encodes the register inside of the opcode */
	if ((insn & 0xc1f80000) == 0x81c00000) {
		unsigned long rd = ((insn >> 25) & 0x1f);

		if (rd <= 15) {
			slot = &regs->u_regs[rd];
		} else {
			/* Hard case, it goes onto the stack. */
			flushw_all();

			rd -= 16;
			slot = (unsigned long *)
				(regs->u_regs[UREG_FP] + STACK_BIAS);
			slot += rd;
		}
	}
	if (slot != NULL)
		*slot = real_pc;
}

/*
 * Called after single-stepping.  p->addr is the address of the
 * instruction whose first byte has been replaced by the breakpoint
 * instruction.  To avoid the SMP problems that can occur when we
 * temporarily put back the original opcode to single-step, we
 * single-stepped a copy of the instruction.  The address of this
 * copy is p->ainsn.insn.
 *
 * This function prepares to return from the post-single-step
 * breakpoint trap.
 */
static void __kprobes resume_execution(struct kprobe *p,
		struct pt_regs *regs, struct kprobe_ctlblk *kcb)
{
	u32 insn = p->ainsn.insn[0];

	regs->tpc = kcb->kprobe_orig_tnpc;
	regs->tnpc = relbranch_fixup(insn,
				     (unsigned long) p->addr,
				     (unsigned long) &p->ainsn.insn[0],
				     regs->tnpc);
	retpc_fixup(regs, insn, (unsigned long) p->addr);

	regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
			kcb->kprobe_orig_tstate_pil);
}

static inline int post_kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *cur = kprobe_running();
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	if (!cur)
		return 0;

	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
		kcb->kprobe_status = KPROBE_HIT_SSDONE;
		cur->post_handler(cur, regs, 0);
	}

	resume_execution(cur, regs, kcb);

	/*Restore back the original saved kprobes variables and continue. */
	if (kcb->kprobe_status == KPROBE_REENTER) {
		restore_previous_kprobe(kcb);
		goto out;
	}
	reset_current_kprobe();
	unlock_kprobes();
out:
	preempt_enable_no_resched();

	return 1;
}

/* Interrupts disabled, kprobe_lock held. */
static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
	struct kprobe *cur = kprobe_running();
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
		return 1;

	if (kcb->kprobe_status & KPROBE_HIT_SS) {
		resume_execution(cur, regs, kcb);

		reset_current_kprobe();
		unlock_kprobes();
		preempt_enable_no_resched();
	}
	return 0;
}

/*
 * Wrapper routine to for handling exceptions.
 */
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
				       unsigned long val, void *data)
{
	struct die_args *args = (struct die_args *)data;
	int ret = NOTIFY_DONE;

	preempt_disable();
	switch (val) {
	case DIE_DEBUG:
		if (kprobe_handler(args->regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_DEBUG_2:
		if (post_kprobe_handler(args->regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_GPF:
	case DIE_PAGE_FAULT:
		if (kprobe_running() &&
		    kprobe_fault_handler(args->regs, args->trapnr))
			ret = NOTIFY_STOP;
		break;
	default:
		break;
	}
	preempt_enable();
	return ret;
}

asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
				      struct pt_regs *regs)
{
	BUG_ON(trap_level != 0x170 && trap_level != 0x171);

	if (user_mode(regs)) {
		local_irq_enable();
		bad_trap(regs, trap_level);
		return;
	}

	/* trap_level == 0x170 --> ta 0x70
	 * trap_level == 0x171 --> ta 0x71
	 */
	if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
		       (trap_level == 0x170) ? "debug" : "debug_2",
		       regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
		bad_trap(regs, trap_level);
}

/* Jprobes support.  */
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct jprobe *jp = container_of(p, struct jprobe, kp);
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	kcb->jprobe_saved_regs_location = regs;
	memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));

	/* Save a whole stack frame, this gets arguments
	 * pushed onto the stack after using up all the
	 * arg registers.
	 */
	memcpy(&(kcb->jprobe_saved_stack),
	       (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
	       sizeof(kcb->jprobe_saved_stack));

	regs->tpc  = (unsigned long) jp->entry;
	regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
	regs->tstate |= TSTATE_PIL;

	return 1;
}

void __kprobes jprobe_return(void)
{
	__asm__ __volatile__(
		".globl	jprobe_return_trap_instruction\n"
"jprobe_return_trap_instruction:\n\t"
		"ta 0x70");
}

extern void jprobe_return_trap_instruction(void);

extern void __show_regs(struct pt_regs * regs);

int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
	u32 *addr = (u32 *) regs->tpc;
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	if (addr == (u32 *) jprobe_return_trap_instruction) {
		if (kcb->jprobe_saved_regs_location != regs) {
			printk("JPROBE: Current regs (%p) does not match "
			       "saved regs (%p).\n",
			       regs, kcb->jprobe_saved_regs_location);
			printk("JPROBE: Saved registers\n");
			__show_regs(kcb->jprobe_saved_regs_location);
			printk("JPROBE: Current registers\n");
			__show_regs(regs);
			BUG();
		}
		/* Restore old register state.  Do pt_regs
		 * first so that UREG_FP is the original one for
		 * the stack frame restore.
		 */
		memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));

		memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
		       &(kcb->jprobe_saved_stack),
		       sizeof(kcb->jprobe_saved_stack));

		return 1;
	}
	return 0;
}

/* architecture specific initialization */
int arch_init_kprobes(void)
{
	return 0;
}